Thermally Enhanced Photoinduced Reorientation in Photo-Cross-Linkable Liquid Crystalline Polymers Comprised of Cinnamate and Tolane Mesogenic Groups

Photo-cross-linkable liquid crystalline polymers (PLCPs) comprised of a 4-methoxycinnamoyloxy group connected with a tolane moiety possessing methyl substituents were synthesized in order to investigate the influence of methyl substituents on the thermally enhanced in-plane molecular reorientation of thin films. Different wavelengths from a UV light source were used to evaluate the effect of the photoreaction of the cinnamate and tolane moieties. For all PLCP films, thermally enhanced photoinduced molecular reorientation was observed, but the reorientation order and its direction greatly depended on the position and the number of the methyl substituents as well as the wavelength of light. A smaller degree of photoreaction was sufficient for effective molecular reorientation when the photoreaction of the tolane moiety was restricted.